This invention relates to a recalibration system for a light emitting diode (LED) array for use in a print head of a line printer.
A print head of a line printer may comprise an array of LED arranged in a line which may be as long as one meter, the line being composed of a tightly packed LED array with each LED providing one pixel of the image to be produced with 600 pixel per inch. It is a known problem that a tight tolerance in uniformity of light output in such a high quality print head is difficult to achieve and even more difficult to maintain. As diodes degrade at different rates, an internal recalibration system is essential to a printer with an expected life &gt;10,000 hours. Calibration systems are known, see for example U.S. Pat. No. 4,596,995 which require a usual inspection of intensity levels by a human operator; such systems would not be suitable for a recalibration system which can be operated automatically on a daily basis.